1. Technical Field
The present invention relates to a vibration-free handle adapted for use on a vibrant tool such as a jack-hammer or a pneumatic drill, and particularly to a vibration-free handle which is provided with a novel vibration isolator.
2. Background Art
In using a hand-operated vibration tool such as a jack-hammer or a chain saw, it has been a serious problem to damp vibrations from the tool since vibrations of certain frequency, generally between 60 and 100 Hz, are harmful to tool operators. One widely known device for damping vibrations from a tool is a rubber cushion, which is disposed between the vibrant tool and a handle mounted thereon. Another is a vibration preventive device which includes springs. In these devices, vibration isolation is achieved by lowering the natural vibration frequency of the handle to a value less than the exciting frequency of the tool. Therefore, the weight of the handle has to be raised in order to reduce the vibration, if satisfactory vibration isolation is desired, or the elastic coefficient of the rubber cushion or the springs has to be lowered. However, in the former case, the total weight of the tool increases, and in the latter case, handling of the tool becomes difficult since the connection between the tool and the handle becomes too soft.
Also, from another point of view, conventional vibration isolators have been insufficient. The vibration consists of three-dimensional elements of vibrations. Here, the direction the tool vibrates is called a "z-direction"--this direction is considered a "vertical direction" in this specification--and two directions perpendicular to the z-direction are respectively called a "x-direction" and a "y-direction"--these two directions are considered extending horizontally and the y-direction represents the direction the handle grip extends. The conventional vibration isolators are only satisfactory in absorbing the vibration elements in z- and x-directions.